1. Field of the Invention
The subject matter of this invention is related generally to expulsion type fuses and in particular to expulsion type fuses having condensers associated therewith.
2. Description of the Prior Art
It is known to provide a closed condenser at the end of expulsion type fuse where the condenser has a cooling means therein for cooling and condensing hot gases which may exit the expulsion type fuse. Condensers of this type are described in U.S. Pat. No. 2,077,276, issued to J. Slepian on Apr. 13, 1937 and U.S. Pat. No. 2,184,760, issued to J. M. Wallace on Dec. 26, 1939. Generally the exit gas from the expulsion type fuse is cooled by the cooling means, which may comprise copper tubes or the like disposed in the condenser, thus providing liquid water and a residual gas. In known types of expulsion type fuses, compressed boric acid is utilized in the expulsion type fuse because of certain unique and desirable characteristics. Under the influence of the electric arc the boric acid, which has the chemical formula H.sub.3 BO.sub.3, decomposes into water (H.sub.2 O) and boric anhydride (B.sub.2 O.sub.3). The hot boric anhydride gas has a tendency to produce high pressure within the condenser. Consequently, in any situation where it is desirous that the gaseous products in the condenser do not escape to the outside environment the sealing of the condenser must be carefully completed. Often this is costly, time consuming and in many instances extremely difficult. Furthermore, the hot exit gas from the expulsion type fuse has a tendency to partially destroy a portion of the copper metal screen or a number of the condensing tubes thus introducing small and even microscopic hot or molten particles of electrically conductive material into the boric anhydride gas. Consequently, if the high pressure hot gas leaks out of the condenser, small or microscopic electrically conductive particles may leak with it. Thus, it can be seen that in a situation where it is undesirous for the gases and/or hot particles to excape from the condenser-fuse combination, the prior art condensers present significant problems and disadvantages. One situation where a condenser which leaks gas and/or hot electrically conductive particles is very undesirable is in the submersible expulsion fuse. Other arrangements which are interesting when considering the prior art are disclosed in U.S. Pat. No. 2,647,970, issued to W. S. Edsall et al on Aug. 4, 1953, U.S. Pat. No. 3,368,047, issued to C. McClure, Jr. on Feb. 6, 1968 and U.S. Pat. No. 3,723,930, issued to R. E. Koch on Mar. 27, 1973. An expulsion type fuse which has no condenser is taught in U.S. Pat. No. 3,855,563, issued to F. L. Cameron et al on Dec. 17, 1974.